Yep I've been having 'fun' with this as well, the only way I've got it to work so far is to use my WinXP box to download a file from shoutcast.com on the desktop and then manually type in the URL in Amplifier. (Even this slow method sometimes fails for some streams)

You should be able to setup IBrowse so that you can click the streams directly, I tried this on shoutcast.com (had to go to the older classic site to see anything) and although I could get Amplifier to startup automatically I couldn't get it to play any streams!

Both AminetRadio and AmigaAMP are no good to me because of AHI which runs like a dead dog on my system (even when running at the worst quality).